体会、分析抽象类的作用

 #include<iostream.h>
class Vehicle
{
public:
 virtual void run()=0;
};
class Car:public Vehicle
{
public:
 virtual void run(){cout<<"run a car\n";}
};
class Airplane:public Vehicle
{
public:
 virtual void run(){cout<<"run a airplaane\n";}
};
void main()
{
 Vehicle *pt;
 Car ca;
 Airplane ai;
 pt=&ca;pt->run();
 pt=&ai;pt->run();
}